after killing quelaag if you go down stairs after ringing the bell there is a circular thing with a raised circle in the center. if you search around you will find a hidden wall with this egg carrier talk to him and answer yes then talk to quelaan, quelaags sister and you can join the covenant

the cat cov. ring if you put it on you can randomly invade in the forest from anywhere in the world. once the invading message comes up you can swap rings before you get sent away.